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Down's syndrome

Down's syndrome is a genetic disorder that was named after John Langdon Down, the doctor who first recognised it as a distinct condition in 1866.

Down's syndrome affects a baby's normal physical development and causes mild to moderate learning difficulties. It is a lifelong condition that develops when a baby is still in the womb (uterus).

Children who are born with Down's syndrome also have a higher chance of developing other conditions, some of which are life-threatening. For example:

congenital heart disease - a general term that describes a series of birth defects that affect the heart

sight and hearing problems

Alzheimer's disease - a common form of dementia (a deterioration of mental abilities, such as memory and reasoning) that often affects people who are over 65 years of age

How common is Down's syndrome?

About 1 in every 550 live births in Ireland is affected by Down's syndrome.Down's syndrome affects all ethnic groups equally. Boys are slightly more likely (around 15%) to be born with Down's syndrome than girls.

With every pregnancy, there's a small chance of having a baby who has Down's syndrome.

Some people are more likely to have a child with Down's than others.

The main thing that increases the chance of having a baby with Down's syndrome is the mother's age.

Outlook

The outlook for Down's syndrome can vary widely, depending on whether a child with the condition also develops any other serious health conditions.

Children with Down's syndrome are most vulnerable during the first year of their life. About 15% of children with Down's syndrome will die during the first year, usually from a complication that arises from congenital heart disease.

After the first year of life, the outlook for children with Down's syndrome improves dramatically. Due to advances in treatment, the average life expectancy for a person with Down's syndrome is around 50, and this may well improve in the future.

Every child's personality is different, and it is important never to stereotype a person with Down's syndrome. However, in general terms, people with Down's syndrome tend to have warm, gentle and cheerful personalities, despite the day-to-day problems they have to face.

Chromosome

Chromosomes are the parts of a body cell that carry genes. A human cell usually has 23 pairs of chromosomes.

Geneticdisorder

A genetic disorder is a disorder caused by a fault in the genes. It is usually hereditary (runs in the family).

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The symptoms of Down's syndrome can affect a person in many different ways. However, the most obvious symptom of the condition is its effect on a person's physical appearance.

Physical appearance

People with Down's syndrome tend to have a number of typical physical features. Some people with the syndrome only have a few of these features, while others are more severely affected.

The physical features of Down's syndrome may include:

eyes that slant upwards

small ears

flat back of head

small mouth

protruding tongue

flattened nose bridge

white spots on the iris (the coloured part of the eye), known as Brushfield spots

short fingers

broad hands with a single crease across the palm

loose skin on the back of the neck

loose joints (babies in particular may seem 'floppy')

poor muscle tone (hypotonia)

low birth weight

vertical skin folds (epicanthic folds) between the upper eyelids and inner corner of the eye

Learning difficulties

All children will Down's syndrome will have learning difficulties, which can range from mild to moderate.

One way of measuring a person's intelligence is to use a type of test called an intelligence quotient (IQ). An IQ test involves exercises that are designed to assess specific capabilities.

The average IQ score for the general population is 100. People with Down's syndrome have an IQ of 25 to 80, with an average score of 50.

In particular, children with Down's syndrome may have:

memory problems - both short-term and long-term memory

concentration problems - many children have low attention spans

difficulty problem solving

difficulty understanding the consequences of their actions

Delayed development

Children with Down's syndrome have delayed physical and mental development.

Children with Down's syndrome are usually much shorter than other children their age. Growth continues through childhood but most adults with Down's syndrome are below average height - around 158cm (5.2ft) for men and 140cm (4.6ft) for women.

With regards to mental development, children with Down's syndrome usually take longer to reach important developmental milestones, such as:

learning to crawl

learning to walk

learning to speak

learning to read

learning the social skills that are used for social interaction

It is important to recognise that a child with Down's syndrome may still be able to acquire most, if not all, of the mental and social skills that most other people develop. Their development simply occurs at a slower pace.

Joint

Joints are the connection point between two bones that allow movement.

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Down's syndrome is a genetic condition that occurs as a result of an extra chromosome.

Chromosomes

Chromosomes are blocks of deoxyribonucleic acid (DNA) that are found in every cell in the human body. Chromosomes contain a detailed set of genetic instructions that control a wide range of factors, including:

how the body's cells develop

the colour of a baby's eyes

the sex od a baby

A healthy person inherits 46 chromosomes from their parents - 23 from their mother and 23 from their father.

Chromosome 21

Down's syndrome is caused by abnormalities that affect the twenty-first chromosome, known as chromosome 21.

Chromosome 21 can be affected in three main ways, leading to the three main sub-types of Down's syndrome. These are explained below.

Full trisomy 21 Down's syndrome is the most common type of Down's syndrome, accounting for 94% of all cases. Full trisomy 21 develops because every cell in the body has an extra copy of chromosome 21 (trisomy is a Greek word that means 'third copy').

Mosaicism Down's syndrome is the least common type of Down's syndrome, accounting for 2.5% of all cases. In cases of mosaicism Down's syndrome, some but not all cells have an extra copy of chromosome 21. The symptoms of mosaicism Down's syndrome tend to be milder and less wide ranging compared with the other types.

Translocation Down's syndrome - is caused when a piece of chromosome 21 attaches itself to another chromosome in a cell. It accounts for 3.5% of cases of Down's syndrome. The symptoms of translocation Down's syndrome are similar to those of full trisomy 21 Down's syndrome but, unlike this form of the condition, it is occasionally possible for a parent to pass translocation Down's syndrome on to their child (see below).

It is thought that some people do not have symptoms of translocation Down's syndrome but they have altered genetic material that can trigger the condition in their children. These people are known as translocation carriers.

The risk of a translocation carrier passing on the condition to their child depends on their sex (this is due to the way that chromosomes are passed down through families). That is:

male carriers have around a 1 in 35 chance of passing on the condition

female carriers have around a 1 in 8 chance of passing on the condition

However, it is thought that most cases of translocation Down's syndrome are not inherited in this way.

Effects of chromosome 21

The extra copy of chromosome 21 in children with Down's syndrome leads to many parts of their body not developing properly.

Chromosome 21 is the smallest of all the chromosomes, but it still contains more than 300 different genes (units of genetic material). It is thought that many of the genes play an important role in the development of key functions of the body, including:

the development of the heart

the development of the brain

the development and regulation of the metabolism (the rate at which the body uses energy)

Chances of having a baby with Down's Syndrome

With every pregnancy, there's a small chance of having a baby who has Down's syndrome.

Some people are more likely to have a child with Down's than others.

Maternal age

The main thing that increases the chance of having a baby with Down's syndrome is the mother's age.

For example, a woman who is:

20 years of age has a 1 in 1,500 chance

30 years of age has a 1 in 800 chance

35 years of age has 1 in 270 chance

40 years of age has a 1 in 100 chance

45 years of age has a 1 in 50 or greater chance

However, most babies with Down's syndrome are born to mothers who are under 35 years of age. This is due to the fact that women under 35 make up the majority of the child-bearing population.

Environmental factors

There is some evidence to suggest that 'clustering' of new cases of Down's syndrome does occur. Clustering means that an above-average number of cases develop over a short to medium period of time in one specific geographical area, such as the district of a city, or in a village.

This clustering of Down's syndrome cases could be the result of chance, but some researchers have suggested that there may be certain environmental factors that increase the risk of the condition. Such factors include:

exposure to infectious agents, such as viruses, during pregnancy

using oral contraception

smoking during pregnancy

exposure to radiation

exposure to pesticides

living near waste-disposal facilities, such as landfill sites or waste incinerators

There is little in the way of hard evidence to support any of the suggestions listed above. However, smoking is known to increase the risk of stillbirth, miscarriage and premature birth.

Further research is required in order to confirm or disprove whether environmental factors play a role in Down's syndrome.

Brain

The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Chromosome

Chromosomes are the parts of a body cell that carry genes. A human cell usually has 23 pairs of chromosomes.

Genes

Genes contain information that you inherit from your parents, such as eye or hair colour. They are carried by chromosomes.

Genetic

Genetic is a term that refers to genes- the characteristics inherited from a family member.

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Antenatal screening is a way of assessing whether your unborn baby could develop, or has developed, an abnormality during your pregnancy.

Antenatal screening cannot diagnose conditions such as Down's syndrome, but it can determine the likelihood of your baby developing the syndrome.

If the risk of Down's syndrome (or any other condition) is shown to be high, further testing can be arranged to confirm whether or not your baby has the condition. The test that is used for Down's syndrome is a combined blood test and an ultrasound scan, which is known as the 'combined test'.

Blood test

During a blood test, a sample of your blood will be taken and tested to check the levels of certain proteins and hormones. If your blood contains abnormal levels of these substances, you may have an increased risk of having a baby with Down's syndrome.

Nuchal translucency

You will have a number of ultrasound scans throughout your pregnancy to check the development of your baby. An ultrasound scan is a painless procedure that uses high-frequency sound waves to produce a picture of the inside of your body (in this case, your womb).

In order to screen for Down's syndrome, you will have a special type of ultrasound scan known as nuchal translucency. This type of ultrasound works in the same way as a normal ultrasound scan, but it focuses on measuring the space between the spine and the nape (the back of the baby's neck).

All babies tend to collect fluid behind the neck. However, babies with Down's syndrome usually have more fluid in their neck than normal. Measuring the thickness of fluid will help to determine whether your baby is likely to have Down's syndrome.

Timing

You should ideally have antenatal screening for Down's syndrome by the end of your first trimester (13 weeks and six days). Most women are screened between 11 to 13 weeks. However, if necessary, it is possible to have screening up to 20 weeks into your pregnancy, although you may also need more blood tests.

Diagnostic tests

If the results of your antenatal screening or ultrasound scan suggest that your baby may be at an increased risk of a particular health problem or condition, such as Down's syndrome, you may be advised to have further tests.

There are two types of test that can help to diagnose potential health problems or conditions while your baby is still in the womb. These are:

chorionic villus sampling (CVS)

amniocentesis

It is important to be aware that both of these diagnostic tests can, in uncommon cases, result in complications. Your GP or midwife can discuss all of your options with you in detail.

Chorionic villus sampling (CVS)

Chorionic villus sampling (CVS) involves taking a small sample of the placenta for closer examination. The placenta is the organ in which the foetus develops and is protected and nourished.

CVS can be performed after 10 weeks of pregnancy. The sample is taken either by passing a thin needle through the wall of your abdomen (tummy), or by passing a small tube through your vagina and the neck of your womb (cervix).

The needle or tube is guided into the correct position using an ultrasound scan. After the sample has been taken, it will be sent to a laboratory for testing. The results will show whether your baby has Down's syndrome.

Possible complications of CVS can include:

infection

heavy bleeding

miscarriage

It is estimated that approximately 1 in every 100 woman will have a miscarriage after having CVS.

Amniocentesis

Amniocentesis involves taking a small sample of amniotic fluid (the fluid that surrounds the foetus in the womb) for examination.

Amniocentesis is usually carried out after week 15 of pregnancy, and it can be carried out up until week 22. The sample of amniotic fluid is taken by passing a needle through your abdomen (tummy) and womb. The sample is drawn out through a syringe.

As with CVS, the needle is guided into the correct position using an ultrasound scan. After the sample of amniotic fluid has been taken, it will be sent to a laboratory for testing.

Possible complications of amniocentesis can include:

infection

injury to you or your baby

As with CVS, there is also a 1 in a 100 chance of having a miscarriage after the procedure.

Counselling

Being told that your baby may have Down's syndrome can be difficult news to deal with. You will therefore be offered counselling so that you and your partner can express your feelings and ask questions about how this diagnosis may affect you both.

Diagnosis after birth

Once your baby is born, the initial diagnosis of Down's syndrome is usually based on your baby's physical appearance. Your doctor will assess your baby and look for the typical physical features that are associated with the condition, such as eyes that slant upwards or a flat back of the head.

If your doctor needs to definitively diagnose Down's syndrome, they will arrange for a blood test known as a chromosomal karyotype. A sample of your baby's blood will be taken and sent to a laboratory so that the chromosomes in the blood can be analysed. If the blood test finds that there is an extra chromosome 21, your baby will be diagnosed with Down's syndrome.

Blood test

During a blood test, a sample of blood is taken from a vein using a needle, so it can be examined in a laboratory.

Chromosome

Chromosomes are the parts of a body cell that carry genes. A human cell usually has 23 pairs of chromosomes.

Gene

Genes contain information that you inherit from your parents, such as eye or hair colour. They are carried by chromosomes.

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Reliability of screening

As with most medical tests, the tests that are used to screen Down’s syndrome have a reasonably high level of accuracy, but they are not completely accurate.

Two main mistakes can be made during any medical test:

a false-positive result, where a test produces a positive result, such as a child having Down’s syndrome, but the result is negative in reality, i.e. the child does not actually have Down’s syndrome

a false-negative result, where a test gives an ‘all-clear’ by indicating that no problems have been found, but in reality the test has failed to detect a problem, such as the child having Down’s syndrome

The false-positive and false-negative rates of the various tests used in screening are listed below.

Blood tests - have a false-positive rate of 3-5% (which means that three to five children out of 100 who are tested will be diagnosed as having Down’s syndrome when they do not). The false-negative rate is 35% (which means that for every 100 cases where a child has Down’s syndrome, the diagnosis will be missed in 35 children).

Nuchal translucency ultrasound scan has a false-positive rate of 3.5-5%, and a false-negative rate of 30%.

Chorionic villus sampling (CVS) has a false-positive rate of 1-2%, and a false-negative rate of 2%.

Amniocentesis has a false-positive rate of 0.1-0.6%, and a false-negative rate of 0.6%.

No single test is entirely accurate, which is why a combination of different tests can be used for screening. However, the more invasive tests, such as CVS and amniocentesis, run a small risk of causing a miscarriage (1 in 100).

Another important factor is that the false-positive rate of a test is usually the most important factor in assessing its reliability. This is because it is much more unlikely that a child has a rare condition, such as Down’s syndrome, which means that a false-positive result is more likely.

Carefully discuss with your GP and antenatal care team the risks involved with testing, and the implication of the results.

There is no cure for Down's syndrome, but there are a number of treatments that can help someone with the condition to lead a healthy, active and more independent life.

Emotional impact

In some cases, it may not be apparent that a baby has Down's syndrome until after they are born. Giving birth can be exciting, scary and tiring, and finding out that your baby has Down's syndrome can be an unexpected shock.

If you have recently found out that your child has Down's syndrome, you may feel a range of emotions, such as fear, sadness or confusion. Some people feel numb, while others feel immediately protective towards their child.

There is no right or wrong way to react after discovering that your child has Down's syndrome. Finding out more about the condition will give you a better understanding about how it may affect your child's life, as well as your own. Many parents find it reassuring to learn more about Down's syndrome.

Support groups

If your child has Down's syndrome, it is important to remember that you are not alone in your situation. Five thousand people in Ireland have Down's syndrome. Also, many people, such as family members, carers and friends, have experience in supporting and caring for those with the condition.

You may find it helpful to talk about your experiences with other families. They can offer you advice and talk through any fears or concerns that you may have.

If you cannot find an appropriate support group, your GP should be able to put you in touch with one. Down Syndrome Ireland http://www.downsyndrome.ie/ also provides information and support for people with Down's syndrome, as well as their families and friends.

Early intervention

Early intervention programmes are specifically designed for children with disabilities and learning difficulties. They focus on providing support to babies and children with Down's syndrome, from when they are born until they are five years old.

Early intervention programmes provide healthcare, education and treatments, such as speech therapy and physiotherapy. They also give advice and support to the family looking after the child.

Early intervention is important because the earlier a child with Down's syndrome receives the necessary help and support, the more independent and healthy they are likely to be later in life.

Care team

There are a number of different healthcare professionals who will monitor and treat someone with Down's syndrome. These may include the following:

Physiotherapist

A physiotherapist is a trained healthcare professional who uses physical methods, such as massage and manipulation, to promote health and wellbeing.

A child with Down's syndrome will often have physiotherapy from a young age because it can help them to improve their range of movement. Babies with Down's syndrome may have poor muscle tone, so a physiotherapist can help them to learn to roll over, sit up or walk.

Speech therapist

Children with Down's syndrome may have problems learning to speak, so a speech therapist can help them to learn to communicate more effectively.

Occupational therapist

Occupational therapists give people practical support so that they can live more independently. For example, due to poor muscle tone (hypotonia) many people with Down's syndrome have problems with tasks that require a certain degree of physical co-ordination, such as feeding and dressing.

An occupational therapist can help a person with Down's syndrome by breaking down tasks into smaller steps, then helping them to learn how to complete the task, step-by-step.

See the Health A-Z topic about Occupational therapy for more information about this type of treatment.

Dietitian

People with Down's syndrome may find it difficult to control their weight. Rates of obesity are particularly high among adults with Down's syndrome. An estimated half of all adults with Down's syndrome are obese.

The reasons for this are uncertain, but a combination of factors may be responsible; for example, having an underactive metabolism, which makes it more difficult to burn off calories, and leads to a less physically active lifestyle than those without the condition.

A dietitian (an expert in food and nutrition) can help someone with Down's syndrome to devise a dietary plan that is tailored to their needs. This will ensure that they are eating a healthy, nutritious and well-balanced diet.

GP

Your GP will help you to deal with any general health problems and some of the day-to-day management of Down's syndrome.

Social worker

People with Down's syndrome may need help in overcoming social problems, such as finding accommodation or applying for financial benefits. A social worker will help them to do this, enabling them to live more independently.

Audiologist

People with Down's syndrome sometimes have hearing problems - see Down's syndrome - complications. An audiologist (an expert in diagnosing and treating hearing conditions) will monitor your hearing in order to detect problems as soon as possible.

Ophthalmologist and orthoptists

An ophthalmologist is a health professional who specialises in treating eye conditions. People with Down's syndrome have an increased risk of developing eye problems, such as eye infections and cataracts.

An orthoptist often works with an ophthalmologist to treat eye conditions that involve problems with eye movement and focusing ability, such as squints (strabismus) or 'lazy eye' (amblyopia).

Paediatrician

A paediatrician is a doctor who specialises in treating children. They will often help to co-ordinate all of the different types of treatment that your child needs.

Cardiologist

A cardiologist is someone who specialises in diagnosing and treating heart conditions. People with Down's syndrome have an increased risk of developing heart problems, so their heart must be checked regularly.

Monitoring

Children and adults with Down's syndrome need regular check-ups so that their health can be closely monitored.

As those with Down's syndrome are more likely to develop health problems, such as cataracts and hearing problems, it is very important to carefully monitor their health so that any problems can be detected and treated as soon as possible.

Someone with Down's syndrome will usually have their sight, hearing and thyroid function (a test to determine whether the thyroid gland is releasing the right amount of hormones into the body) regularly checked. Children with Down's syndrome will also have their growth monitored.

Living independently

With help and support, many people with Down's syndrome can live an active and independent life.

Many children with Down's syndrome are able to go to mainstream schools. However, if your child is severely affected by Down's syndrome, or you feel that they would benefit more from specialist schooling, there are a number of schools and other facilities that offer schooling specifically tailored to those with special needs.

Many young adults with Down's syndrome pursue further education. Some also gain employment, usually on a part-time basis, although this will depend on the individual. Many people with Down's syndrome enter loving relationships, although they may need guidance and support when it comes to things such as contraception.

Women with Down's syndrome tend to have a reduced fertility rate. This does not mean that they cannot conceive children, but it does make it more difficult. Those who decide to have children will usually need specialist guidance and support to help them cope with the physical and mental demands of a newborn baby. Most men with Down's syndrome are infertile.

If a woman has Down's syndrome, the chance of their child also having the condition is 35-50%. It is difficult to estimate the risk if both parents have the condition because most men are unable to have children. The risk of miscarriage and premature birth is also much greater in women who have Down's syndrome.

Although someone with Down's syndrome may never be able to live completely independently, many people with the condition can live on their own or with someone else. In most cases, people with Down's syndrome move into property that is owned and staffed by a housing association. The staff provide different levels of support, depending on the individual's particular needs.

Glossary

Bacteria

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.

Blood vessels

Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Hearing tests

Audiometry is any testing that checks hearing.

Heart

The heart is a muscular organ that pumps blood around the body.

Immunisation

Vaccination or immunisation is usually given by an injection that makes the body's immune system produce antibodies that will fight off a virus.

Physiotherapy

Physiotherapy is a treatment that uses physical movements, massage and exercise to relieve illness or injury.

Thyroid

The thyroid is a jointed piece or cartilage that enclosed the vocal cords and forms the 'Adam's apple' in men.

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Some people with Down's syndrome have very few health problems as a result of their condition. However, other people can be more severely affected and will need extra medical care and attention.

People with Down's syndrome are at an increased risk of developing a number of conditions and health problems. Some of these are outlined below.

Heart defects

Around 40-50% of children with Down's syndrome have a congenital heart defect. Around 60% require treatment in hospital. A congenital defect means that you are born with it.

There are several different heart problems that can affect people with Down's syndrome. The most common types of congenital heart disease are known as septal defects, which account for 9 out of 10 cases.

A septal defect is where a hole develops inside one of the walls that separate the four chambers of the heart. The heart has two lower chambers known as the left and right ventricles, and two upper chambers called the left atrium and the right atrium.

Septal defects, often referred to as 'a hole in the heart', can cause a build-up of blood in one or more of the heart's chambers. This can place extra strain on the heart because it has to work harder to pump blood through the four chambers.

Less common serious types of congenital heart disease in people with Down's syndrome include:

tetralogy of Fallot , which accounts for 6% of cases

patent ductus ateriosus, which accounts for around 4% of cases

Tetralogy of Fallot is a combination of four different heart defects that causes a lowering of oxygen levels in the blood. This can lead to symptoms of breathlessness.

Patent ductus ateriosus (PDA) is a duct or passage in the heart that usually closes shortly after birth. However, in cases of PDA, the duct fails to completely close, which means that oxygen-rich blood that is meant to be pumped away from the lungs leaks back through the duct and into the lungs.

This can place strain on the heart and the lungs because they have to work harder to compensate for the problems caused by the duct.

If your baby is diagnosed with Down's syndrome, their heart will be carefully assessed so that any heart defects can be detected and treated as soon as possible. In around 30% of cases, the heart defect is serious and may require immediate surgery. In other cases, the heart can be monitored and treated at a later date, if necessary.

Minor septal defects can usually be treated with minor surgery. Larger defects will need open heart surgery to correct. Tetralogy of Fallot usually requires open heart surgery, and several operations may be needed to restore normal heart function. PDA can usually be treated with medication that encourages the duct to close.

Hearing problems

Around 50% of people with Down's syndrome have problems with their ears and hearing.

Glue ear is a condition that commonly affects people with Down's syndrome. It is caused by a build up of fluid in the middle ear. In some cases, the fluid thickens and makes sounds appear muffled and distorted.

If your child has a hearing problem, they may find it difficult to learn and interact with other children. If your child has glue ear as a result of Down's syndrome, they will usually be referred to an ear, nose and throat (ENT) specialist for treatment.

Vision problems

Around 50% of people with Down's syndrome also have problems with their eyesight.

A squint, which is a condition where one eye turns inwards, outwards, upwards or downwards, is common in people with Down's syndrome, but can usually be successfully treated by wearing glasses. But occasionally, surgery may be used to correct a squint.

Other eye problems can include:

lazy eye - where one eye does not develop fully so loses some focusing ability

Oral health

periodontitis - an infection of the gums and surrounding tissue and bone

People with Down's syndrome often have poor levels of oral health because:

they may find it difficult to brush their teeth

they often have lower levels of saliva than most people, and saliva provides some protection against bacteria

It is recommended that all people with Down's syndrome regularly brush their teeth with a high-fluoride toothpaste (your pharmacist can advise you about this).

People with Down's syndrome may find using an electric toothbrush easier than using a manual one. Those who have particularly severe Down's syndrome may need to have help brushing their teeth.

Thyroid problems

Around 10% of people with Down's syndrome have problems with their thyroid gland. The thyroid gland is located in the neck and is responsible for controlling your metabolism (the rate at which your body uses up the energy). It does this by releasing thyroid hormones into the body.

Most people with Down's syndrome have hypothyroidism, which means their thyroid gland is under-active because it does not produce enough hormones. Symptoms of an under-active thyroid gland can include:

In rarer cases, people with Down's syndrome can also develop hyperthyroidism, which means their thyroid gland is over-active and produces too much thyroid hormone. Symptoms of hyperthyroidism can include:

hyperactivity

difficulty breathing

mood swings

difficulty sleeping

lethargy (lack of energy)

muscle weakness

the need to pass stools or urine frequently

Increased susceptibility to infection

People with Down's syndrome are 12 times more likely to develop an infection compared with the general population, particularly the lung infection pneumonia. This is because their immune system (the body's natural defence against infection) has not developed properly.

Leukaemia

Children with Down's syndrome have an increased risk of developing acute leukaemia, which is a form of cancer that affects the white blood cells (the cells responsible for fighting infection and protecting against it).

Some research suggests that children with Down's syndrome are 56 times more likely to develop acute leukaemia before the age of five, compared with children who do not have the condition.

Even though a child with Down's syndrome has an increased risk of developing leukaemia, it does not necessarily mean that they will develop the condition. For example, only 1 in 100 children with Down's syndrome go on to develop acute leukaemia.

Intestinal problems

Many people with Down's syndrome have some sort of intestinal problem. Some problems are mild and are common in people with and without Down's syndrome. For example, constipation,diarrhoea and indigestion are all common.

However, people with Down's syndrome are more likely to have more significant intestinal problems, such as small bowel obstruction, which stops food passing from the stomach into the large bowel.

An estimated 5-15% of people with Down's syndrome will develop coeliac disease, which is a condition where a person has an intolerance to gluten, a type of protein found in most cereals.

Conditions such as imperforate anus (where a baby is born without an anal opening), or Hirschsprung's disease (where the large bowel is unable to push faeces towards the anus) are relatively rare, but are slightly more common in children with Down's syndrome. For example, approximately 2% of babies with Down's syndrome develop Hirschsprung's disease.

Psychological and behavioural conditions

Around 1 in 5 people with Down's syndrome will develop a psychological or behavioural condition.

Dementia

People with Down's syndrome are more likely to develop dementia when they get older and, in particular, a type of dementia that is known as Alzheimer's disease.

Alzheimer's disease attacks nerves, brain cells and neurotransmitters (chemicals that carry messages to and from the brain).

This can lead to a progressive loss of mental function, and causes symptoms such as:

confusion

poor memory and forgetfulness

mood swings

speech problems

Compared to the rest of the population, people with Down's syndrome tend to develop Alzheimer's disease at an early age. Approximately 40% of 50 to 59-year-olds with Down's syndrome develop Alzheimer's disease. Two thirds will develop Alzheimer's disease by the time they reach 60.

A number of medications, such as donepezil and rivastigmine, can be used to slow down the loss of mental function, but it is currently uncertain whether these medications are effective in people with Down's syndrome. Further research is required.

Dysphagia

Many older people who have Down's syndrome will develop problems with eating, drinking and swallowing. The medical term for this is dysphagia.

Dysphagia can be caused by a number of factors, such as a complication of severe Alzheimer's disease or the wasting of the muscles that are used in swallowing.

Dysphagia is a potentially serious condition because it is possible for small pieces of food or drink to fall down into the lungs and trigger a serious infection. This is known as aspiration pneumonia and can often be fatal.

Mild to moderate dysphagia can be treated by making simple dietary changes. For example, eating soft foods that are easy to swallow, such as soup or mashed potatoes. However, more severe cases may require the use of a feeding tube.

See the Health A-Z topic about Dysphagia for more information.

Glossary

Brain

The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Chromosome

Chromosomes are the parts of a body cell that carry genes. A human cell usually has 23 pairs of chromosomes.

Congenital

Congenital means a condition that is present at birth- the condition could be hereditary or develop during pregnancy.

Constipation

Constipation is when you pass stools less often than usual, or when you are having difficulty going to the toilet because your stools are hard and small.

Stomach

The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.

Testicles

Testicles are the two oval-shaped reproductive organs that make up part of the male genitals. They produce sperm and sex hormones.

Thyroid gland

The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).

Vomiting

Vomiting is when you bring up the contents of your stomach through your mouth.